1. Field of the Invention
This invention relates to a liquid crystal display and more particularly to injecting liquid crystal material and sealing while preventing damage to transistors, etc. from static electricity in an active matrix type liquid crystal display.
2. Description of the Prior Art
For the past several years, liquid crystal displays have been growing in use, for example, in word processors, televisions, etc., as a display means suitable for smaller size and lighter weight devices.
Recently, the display in these instruments has a great demand for larger picture and higher picture quality, and demands for commercialization of the active matrix type liquid crystal display, in which a larger area and higher density are possible are increasing.
However, since such active matrix type liquid crystal displays of larger area and higher density are being researched and developed based on the conventional small-sized low-density liquid crystal display, various problems are caused by these differences.
Problems in manufacturing are shown below as examples.
FIG. 8 is a manufacturing process diagram of the prior art of a liquid crystal cell of a conventional active matrix type liquid crystal display. A manufacturing process will be described with reference to FIG. 8 which shows steps a through m.
First, in step a, two glass substrates for composing the active matrix liquid crystal display are washed.
Then, in step b, a molecule-orienting film is formed on each of the glass substrates, and in step c, an orientation treatment such as a rubbing method is applied on the surfaces.
Then, in steps d and e, a gap potion and a sealing portion to seal liquid crystal material and formed, and in step f, a glass substrate with an electrode provided for every picture element thereof, and a glass substrate provided with a transparent electrode on one surface, are connected through a common electrode.
These two glass substrates are stacked together, in step g, and in step h are heated and pressurized under specified conditions to harden the sealing portion.
FIG. 9 shows a half-finished product which has been processed through such steps a to h.
In FIG. 9, 1 designates a glass substrate with many electrodes 2 formed vertically and horizontally, and 3 designates a glass substrate with a transparent electrode formed thereon. Reference numeral 4 represents a sealing section and 5 represents a shorting ring. The shorting ring 5 shorts signal portions and gate portions of switching transistors formed on the glass substrate 1 to prevent the switching transistors from being damped by static electricity produced in each of the above manufacturing steps.
As shown by broken lines in FIG. 10, the shorting ring 5 connected to an outer edge portion of the glass substrate 1 is cut off together with the outer edge portion of the glass substrate 1 itself. This step is called a scribing step and is shown as step i in FIG. 8.
Then, as shown in FIG. 11, glass substrate 1 and 3 are placed nearly perpendicularly to the liquid crystal surface in a boat 7, where a liquid crystal material 6 accumulates. Liquid crystal injection port 8, provided at the corner of the glass substrates 1 and 3 stacked together, is immersed to inject the liquid crystal material into the space between the glass substrates 1, 3 as shown as step j in FIG. 8.
After the liquid injection port 8 has been sealed in step k, this part is washed shown in FIG. 8 as step 1, and finally a polarizer is attached as shown in FIG. 8, step m.
In such a manufacturing process, shorting ring 5 is intentionally used to prevent the switching transistors from being damaged due to the static electricity. However, before injection of the liquid crystal material, it is necessary, for facilitating the immersion of the substrate into the boat 7 by decreasing the area of glass substrate 1 and for removing the corner section of the glass substrate which is heavily stained, to scribe the glass substrate in the position where the shorting ring is connected. That is, in the steps after scribing step i, the shorting ring is removed and the signal portions and the gate portion of the switching transistors become insulated. For this reason, in the steps thereafter (step (j) and after), if static electricity is produced, the switching transistors can be damaged. For example, a polarizer has a protective film attached to its surface before being attached to the substrate, but the protective film 9, shown in FIG. 12, must be peeled off after the polarizer has been attached in step m of FIG. 8. This can produce a large quantity of static electricity which may cause the switching transistors to be defective. In such a manufacturing process, in step j the liquid crystal material is injected by a so-called perpendicular method. Because when liquid crystal injection port 8 is immersed, not only liquid crystal injection port 8, but also the whole corner section of glass substrates 1 and 3 around port 8 are immersed, the oil, dust, etc. attached to the corner section of glass substrates 1 and 3 are dissolved in the liquid crystal material accumulated in boat 7, and liquid crystal material 6 becomes gradually contaminated and deteriorates with use. Therefore liquid crystal material 6 must be replaced after being used to some degree. In addition, since the whole corner section of glass substrates 1 and 3 is immersed in liquid crystal material 6, some part of liquid crystal material 6, instead of being injected into the space between the glass substrates through liquid crystal injection port 8, sticks to the surface of the corner section of glass substrates 1 and 3. Thus, in such a manufacturing process, a large quantity of liquid crystal material 6 is lost by contamination, deterioration, or sticking to useless portions of glass substrates 1 and 3.
Manufacturing such a large-area and high-density active matrix type liquid crystal display by the conventional method produces static electricity that can damage the switching transistors. In addition, there is a problem of a large quantity of liquid crystal material being lost uselessly by contamination and deterioration or sticking to the useless sections.